Dewatering agent compositions for sulfide materials

ABSTRACT

An improved dewatering agent for aqueous slurries of mineral concentrates comprising branched dodecylbenzene sulphonic acid used alone or in combination with sodium xylene sulphonate.

INTRODUCTION

This invention relates to an improved process for dewatering a mineralconcentrate.

Ores of various minerals are concentrated by various procedures toprovide mineral concentrates that are further processed to valuablematerials. One of the most widely used methods of concentration ofminerals is that of froth flotation which is applicable to a widevariety of ores including sulfide and non-sulfide varieties. In manyinstances a series of flotations are performed whereby increasinglycleaner concentrates result. After a concentrate has been sufficientlyenriched in mineral values, it may be subjected to further processingsuch as drying and smelting, which processing may be performed atanother location. To subject the concentrate to further processing, itis generally dewatered by filtration or equivalent process such ascentrifugation to remove water therefrom. The removal of water from theconcentrate decreases the costs of shipping when it is processed at anew location. The removal of water also reduces the requirements forenergy consumption when drying is effected.

The commercial procedure for dewatering mineral concentrates generallyinvolved filtration of the aqueous slurry of mineral values arising fromconcentrating the ore by flotation or other concentration process. Theresidual water content of the dewatered mineral concentrate will varywidely depending upon the mineral composition, the procedure ofdewatering employed, the absence or presence of dewatering aid, and thelike.

Certain dewatering aids have been used in the prior processes fordewatering. In some instances, the dewatering aid was not completelyacceptable because it did not reduce the moisture content of thedewatered mineral concentrate adequately. In other instances, thedewatering aid was not substantially adsorbed on the dewatered mineralconcentrate and contaminated the process water, which water is recycledto the mining processes, including that of ore concentration, from wherethe mineral concentrates to be dewatered arise. Contamination of therecycled process water adversely affects ore concentration and otherprocesses associated with mining operation.

Commonly used dewatering agents for dewatering mineral concentrates arethe sodium dialkyl sulfosuccinates described in U.S. Pat. No. 4,153,549.A commercial species of the sodium dialkyl sulfosuccinates is sodiumdioctyl sulfosuccinate, commonly referred to in the trade and hereafteras DOSS.

While effective in copper concentrate and lead filtration applications,concentrated DOSS-containing products suffer from severe handlingproblems caused by "skinning" of the products at air/liquid interfaces.This problem forces DOSS-based products to be sold only in drumquantities (never in bulk), thus causing wastage.

In addition to the disadvantages described above, DOSS is an expensivechemical. If it were possible to provide a dewatering agent as effectiveas DOSS yet which was less expensive and more readily available, anadvance in the art of mineral processing would be afforded.

THE INVENTION

The invention comprises a process for reducing the moisture content ofmineral concentrates subject to dewatering which comprises mixing withan aqueous slurry of said mineral concentrate an effective amount of abranched dodecyl benzene sulphonic acid (hereafter referred to asDDBSA).

This material may be further enhanced in its activity yet, at the sametime, provide a lower cost product by combining it with sodium xylenesulphonate. When combined with the sodium xylene sulphonate, it ispreferred to use DDBSA to sodium xylene sulphonate in a weight ratio of5:1 with a general ratio of DDBSA to sodium xylene sulphonate beingwithin the range of 5:1 to 3:1.

When DDBSA, either alone or in combination with sodium xylenesulphonate, is transported and stored commercially, it is beneficialthat there be incorporated therewith a stabilizing agent comprising awater-soluble alcohol. Preferred stabilizing agents are water-solublepolyhydric alcohols with a most preferred alcohol being ethylene glycol.The amount used to stabilize DDBSA or DDBSA in combination with sodiumxylene sulphonate, will range between 10-50% by weight.

A typical composition used in the practice of the invention isComposition 1 which is set forth below:

    ______________________________________                                        Composition 1                                                                 Ingredients       % by weight                                                 ______________________________________                                        C.sub.12, dodecyl benzene                                                                       50.0                                                        sulfonic acid                                                                 Sodium xylene sulfonate                                                                         10.0                                                        Ethylene glycol   25.0                                                        Tap Water         15.0                                                        ______________________________________                                    

The compositions of the invention are capable of dewatering a widevariety of mineral concentrates although they are most effective indewatering sulfided minerals, particularly copper, lead, and zincconcentrates. They are also useful in dewatering fine phosphate rock.The compositions of the invention may also be used in dewatering coalslurries.

The dosage of the compositions which are effective to provide dewateringof various mineral slurries will, of course, vary upon the particularslurry being dewatered. For purposes of illustration, copper dewateringcan be achieved by using between about 0.3-1 lb./ton of Composition 1.In the case of fine phosphate rock dewatering, good effects can beachieved at dosages ranging between 0.1-0.5 lbs./ton.

THE DRAWINGS

FIGS. 1-3 show Composition 1 compared against DOSS as a dewatering agentfor three different copper slurries.

FIG. 4 shows the advantages of the compositions of the invention vs.DOSS for phosphate dewatering.

FIG. 5 shows the advantages of combining DDBSA with xylene sulphonate toprovide an improved dewatering composition.

EXAMPLES

To illustrate the advantages of the invention, the following arepresented by way of example. The following experimental procedure wasused:

A large copper concentrate sample was split into individual 260 mlsamples. This was done by adding small volumes to consecutive 400 mldisposable beakers in a "back and forth" fashion, thereby compensatingfor bucket classification. The copper slurry used was measured at 61%solids.

Product solutions were added directly to the sample beakers as 10%solutions. The slurries were conditioned with a cone-drive mixer/paddleassembly for 30 seconds following product addition.

The conditioned samples were poured into a filter leaf assembly fittedwith the appropriate cloth and a 1.5" plastic collar. Charging of theleaf assembly was done with the applied vacuum valved off just below theleaf head.

The initial vacuum was adjusted to match the plant vacuum of 22" Hg.Upon engaging the vacuum, a stopwatch was started in order to measureform time. (The form time varied between 45 and 55 seconds, independentof treatment.) Upon reaching a form, a second watch was started, and a2.5 minute vacuum dry time allowed.

The moist cakes were immediately discharged into aluminum pans, the wetweights recorded, and the pans placed in a drying oven. Upon dryingovernight, the dry weights were recorded and the moistures calculated.

EXAMPLE 1

Using the above experimental technique, three different copper slurrieswere tested. These slurries were samples received from three differentcommercial copper mining installations. The results of these studies areshown in FIGS. 1, 2, and 3. Composition 1 was compared against a 70%isopropanol solution of DOSS.

From the Figs., it is evident that at 0.6 lb./ton, Composition 1 is moreeffective than DOSS.

EXAMPLE 2

The test conditions used corresponded to those used commercially in aphosphate mining operation from which the phosphate rock sample wastaken. The test parameters are set forth below:

    ______________________________________                                        Cake thickness:        13/4"                                                  Filtration time:       1 minute                                               Initial applied vacuum:                                                                              12" Hg                                                 % H.sub.2 O in untreated                                                                             13-16%                                                 filter cake:                                                                  ______________________________________                                    

In this comparative test, Composition 1 was compared against a 40% DOSSin an aqueous solution which also contained a branched octyl alcohol.

The results showing the superiority of Comp. 1 v. DOSS are set forth inFIG. 4. Further studies show that products such as Composition 1 arestable under conditions of use and long-term storage are not subject tothe problems encountered when concentrated, expensive DOSS solutions areused.

FIG. 5 shows the advantages of using sodium xylene sulphonate to improvethe activity of DDBSA. This comparative study used the test procedure ofExample 1 and the copper slurry of FIG. 3.

It is understood that the compositions used in the invention may beslightly varied without departing from the scope as described herein.For example, any water-soluble salt of DDBSA or xylene sulphonate may beused. Similarly, related branched chained alkyl groups may besubstituted for the C₁₂ branched chained alkyl group of DDBSA.

Having thus described our invention, it is claimed:
 1. A process forreducing the moisture content of mineral concentrates by subjecting saidmineral concentrates to a dewatering process which comprises mixing withan aqueous slurry of said mineral concentrate an effective dewateringamount of a branched dodecyl benzene sulphonic acid which is combinedwith sodium xylene sulfonate in a weight ratio of between 5:1 to 3:1 andthen subjecting the thus-treated mineral concentrate to a dewateringprocess comprising filtration or centrifugation whereby the moisturecontent of said mineral concentrate is reduced.
 2. The method of claim 1where the ratio of branched dodecyl benzene sulphonic acid to sodiumxylene sulphonate is 5:1.